The wear on a weapon and, hence, the maintenance to be provided depends on the movement of the movable parts and thus the conditions of use of the weapon, such as the number of shots fired. It is therefore important to provide the weapons with devices for counting the shots fired.
The known devices perform a counting based on the detecting of phenomena or a combination of phenomena subsequent to the shot, which phenomena are known as a posteriori, contrary to a priori phenomena which occur prior to the firing of the shot. As an example, the following table contains a list of a priori and a posteriori phenomena occurring during the functioning of a weapon.
A prioriA posterioriLoading into chamberRecoil accelerationReleasing of movable partsMovement of the slidePlacement of the loaderRecocking of the hammerMovement of the safety leverRear impactPressing on the triggerBarrel heatDropping of the hammerSoundMovement of the strikerPressure variation in the chamber or in the barrel
For the most part, the shot counting devices work by analysis of the recoil acceleration experienced by the weapon or an internal part of the weapon following the shot. In the patent literature, the documents U.S. Pat. Nos. 8,387,295; 5,566,486; EP 1 881 292 and U.S. Pat. No. 8,418,388 may be cited where the counting is done on the basis of the signal of the recoil acceleration.
Certain of these devices (U.S. Pat. Nos. 8,387,295; 5,566,486 and EP 1 881 292) use a battery to ensure the energizing of the electronic circuit with possible monitoring of the circuit by a phenomenon connected to the event being detected. The disadvantage of batteries is that this increases the probability of counting error due to a failure or a removal of the battery and this shortens the lifetime of the counting device. Hence, document U.S. Pat. No. 8,418,388 proposes a different solution with recuperation of the energy provided by the movement of a part of the weapon. Document U.S. 2010/0251586 likewise proposes a shot counting device with energizing of the electronic circuit via the electromotive force induced by the displacement of a magnet inside a coil, which is coupled to a moving part of the weapon.
Whether with or without recuperation of energy, the devices which work by detecting a posteriori phenomena have three major technical problems:    1. There is a possible confusion between events, resulting in a counting error. For example, the discrimination between live bullet shots and blank shots can only be done by detecting and/or analyzing the very first milliseconds after the detonation. In fact, a blank shot is characterized in having a phase of acceleration to the front for several milliseconds prior to the recoil. Intrinsic delays in the propagation of the recoil or the movements of parts associated with this recoil, added to the necessary time, make impossible any discrimination free of error. Further, the discrimination between a shot and an impact is not always easy, since the measuring of the mere amplitude of the recoil acceleration does not allow a systematic discrimination between a shot and an impact, in particular one due to dropping the weapon.    2. It is impossible to count dry-firing actuations of the striker, i.e., with no ammunition in the chamber, since the latter are not followed by a recoil acceleration.    3. The device cannot work if the recoil of the weapon used for the detecting, or energizing of the circuit is insufficient, especially in the case of devices recuperating the energy generated by the shot. For example, a weapon held firmly at the moment of firing will not recoil, or not sufficiently. In this case, the counting devices with recuperation of energy will not be able to energize the electronic circuit and therefore count the shot. As another example, a very dirty weapon cannot work properly, even though a shot has been fired. In this case, certain a posteriori phenomena used to detect and/or energize the circuit cannot take place, and then the shot also is not counted. Mention may be made, without being exhaustive, of the aforesaid lack of a recoil, the incomplete closure of the chamber, the absence of a rear impact.